Victor Pasko, professor of electrical engineering along with Jianqi Qin, postdoctoral fellow in electrical engineering, at Penn State jointly with Matthew McHarg, professor of physics and director, United States Air Force Academy Space Physics and Hans Stenbaek-Nielsen, professor of geophysics emeritus, University of Alaska, Fairbanks report their latest findings in Nature Communications.

The article, titled “Plasma irregularities in the D-region ionosphere in association with sprite streamer initiation” describe new observations and modeling results providing fundamental understanding on the initiation mechanism of sprite streamers in the D-region ionosphere, which is a transition region in the altitude range of 60 to 90 km between the earth’s lower atmosphere with dense air and its highly conducting ionosphere. Thunderstorms occasionally produce spectacular optical emissions, known as sprites, in this transition region. Although the streamer nature of sprites has been generally accepted, how these filamentary plasmas (i.e., streamers) are initiated remains somewhat of a mystery. Through comparing observational and modeling results, the reported study presents solid evidence indicating that sprite streamers are initiated from pre-existing plasma irregularities in the D-region ionosphere. This is the first time such plasma irregularities are observed, which have a vertical dimension of a few kilometers and a horizontal dimension of a few hundred meters. These irregularities might have been produced by thunderstorm or meteor effects on the D-region ionosphere. This study also shows that observations of sprite discharges represent a useful remote sensing technique for probing plasma irregularities in the lower ionosphere.